Part of a meteorite was seen to fall on a road (52° 33′ 55″ N., 1° 20′ 23″ W.) in the village of Barwell, Leicestershire, at about 16.20 hrs G.M.T. on 24 December 1965. Fragments have been found over an area some ¾ mile long by ½ mile across, and appear to have been part of a single stone, of which 44 Kg (97 lb) have been recovered. The distribution, impact effects, and crustal morphology of the recovered fragments are described. Barwell is a moderately metamorphosed white olivine-hypersthene chondrite; a chemical analysis, with the derived Wahl norm, and a modal analysis are given, together with optical data and electron-probe analyses of the principal constituent minerals.

26 b-axis oscillation photographs of alkali feldspars of microsyenitic dykes of Southern Greenland are presented. The crystals are rather restricted in composition (Or42·4 to Or35·3) but are rather rich in Ca (up to 14 % An). The range of variation of the optic axial angles, 2 V 45° to 71° (exceptions up to 87°), puts the crystals between sanidine-anorthoclase cryptoperthite and orthoclase microperthite, as classified by Tuttle (1952).

Since the syenitic magma cooled down rather rapidly some peculiarities in the structural state of the alkali feldspars are to be expected. The potassium-rich phase is (nearly) monoclinic. According to the values of the reciprocal lattice angles α* and γ* the sodium-rich phases can be divided into three groups: high-temperature pericline-twinned and high-temperature albite-twinned phases, high-temperature pericline-twinned and low-temperature albite-twinned phases, and high-temperature pericline-twinned and low-temperature albite-twinned phases with nearly identical values of the reciprocal lattice angle γ*.

Several cordierites from pegmatites were found by emission spectroscopy to contain as much as 0·7 wt. % of BeO. Structural crystallographic considerations suggest that the beryl molecule, Be3Al2Si6O18, may have appreciable solubility in the structure of cordierite. Some hydrothermal experiments carried out on this assumption indicated about the same amount of BeO substitution in the magmatic temperature range as is shown by the pegmatite cordierites. The natural BeO-bearing cordierites have distinctive infra-red absorption properties, which are reproduced in the synthetic solid solutions.

Natural Al-Fe-Mn epidotes are divided into Al-Fe and Al-Fe-Mn series.

In the Al-Fe series, a, b, and c increase steadily over the range 0 to 0·9 Fe3+ per formula unit, and more slowly at higher Fe contents. Index variation diagrams show the reverse trend, with indices increasing moderately fast over the range 0 to 0·85 Fe, and faster at higher Fe contents.

In the Al-Fe-Mn series, b increases almost linearly over the range of (Fe, Mn) contents, with Mn causing a larger increase than Fe, whilst a and c increase over the range 0 to 0·9 (Fe, Mn), and then decrease. This curious behaviour is accounted for by the application of crystal field theory. The indices increase linearly over the range 0·8 to 1·5 (Fe, Mn), the optic axial angle depending on (Fe, Mn) content and the ratio Mn/(Fe, Mn).

Thermal and mechanical properties (conductivity, thermal expansion, specific heat, compressibility, and hardness), electromagnetic properties (dielectric constants, conductivity, magnetic susceptibility), and thermodynamic data (S) are also summarized, and estimates given where experimental data are not available.

The basic formula of an amphibole is completely defined by stating the number of sodium atoms in X positions and the numbers of aluminium atoms in Y and Z. These three numbers are coordinates in a compositional space that can easily be represented. The alkali amphiboles are re-defined as having at least one atom of sodium in X in the basic formula unit. A systematic nomenclature for the calciferous and alkali amphiboles is suggested using existing end-member names.

The temperature at which dehydroxylation occurs in amphiboles is thought to be largely dependent on the type of cation that occupies the M3 and M1 sites. Four amphibole types have been studied in which these sites are occupied, in various proportions, by Mg2+ or Fe2+. The temperature of dehydroxylation, in an inert atmosphere, is shown to rise with increasing Mg2+ content in these sites.

A method is presented for use with a 3- or 4-axis stage whereby a biaxial mineral, after being oriented into the cardinal position by means of the inner vertical, NS., and EW. axes, can be placed into an orientation suitable for measurement of the 2 V as required by the Berek method. A table of the necessary manipulations is given. The stereographic projection is only used to determine rotational corrections.

Graphite occurs in the Darkainle nepheline syenite complex, Somali Republic, as small drop-like grains in an altered ankeritic carbonatite; it has been recorded previously from carbonate-bearing nepheline syenites and kimberlites. Experimental evidence indicates that siderite decomposes to a stable association of magnetite and graphite within the PT ranges 500 to 10 000 bars and 455 to 745° C. The graphite in carbonatite and other alkaline igneous rocks may have been formed similarly by the decomposition of siderite or iron-rich carbonates.

Mukherjee's definition of psilomelane, A3X6Mn8O16 of orthorhombic symmetry with the space group P222 and the dimensions determined for a single crystal of the Schneeberg sample, is found true for the psilomelane from Ratanpur, India. The indexing of powder data of the Ratanpur sample with the orthorhombic axes a 9·45, b 13·90, c 5·72 Å is most satisfactory.

An examination has been made of the composition and structural state of the feldspars in each of the units of the Rosses granite complex. The compositions of the plagioclases are systematically related to the compositions of the rocks, but the alkali feldspars are much more uniform as a result of postmagmatic recrystallization. In the granites both alkali feldspar and plagioclase are in low-temperature structural states, but alkali feldspar phenocrysts from one of the porphyry dykes associated with the complex show a higher-temperature state.

Two unusual cavities at a Northumberland colliery are described. Although apparently of tectonic origin they do not seem to be related to any major fault. Sideronatrite, not previously recorded in this country, is thought to result from the alteration of the marcasite and pyrite lining the cavities by underground saline waters. These waters are the source of the baryte and gypsum that are also found in the cavities and of the salt stalactites in the disused roadways of the colliery.

There are two outcrops of rhodonite rock at the same stratigraphical horizon in Lower Carboniferous rocks in the Railway Quarry at Meldon. One of these is zoned outwards from rhodonite, through calc-silicate hornfels to quartzite. Well-formed crystals occur in drusy massive rhodonite; examples have been measured and drawn.

The estimation of molybdenum and tungsten when present together has proved difficult, as is indicated by the large number of methods put forward for their determination. Many of the methods given are for one or other of these elements only, a note often being added that the presence of the other invalidates the method. The estimation of molybdate and tungstate in the mineral powellite has been briefly described by one of the authors (A. A. M.): molybdate and tungstate were precipitated as oxinates (Mo,W)O2(C9H6ON)2 and the molybdate (MoO4″) determined by measurement of the optical density at 230 mµ of a solution containing molybdate and tungstate. The amount of tungstate present was then estimated by difference. The property of the molybdate ion, MoO4″, to absorb strongly in the ultra-violet has been further investigated and it has been found that, if a wave-length of 240 mµ is chosen and the proper precautions taken, the MoO4″ ion can be estimated without significant interference by the WO4″ ion. Methods are given for the analysis of the common molybdate and tungstate minerals, together with results obtained during the course of this investigation.

Apparatus using cold-seal pressure vessels of molybdenum-0·5 %-titanium alloy, where each vessel is protected from oxidation by an argon gas jacket, is described. At 1000 bars pressure these vessels can be used for long runs at temperatures up to 1200° C, an increase of approximately 300° C over the range of conventional Stellite vessels. The possible use of other alloys to extend the range of this type of apparatus further is briefly discussed; pure tungsten has been shown to be too brittle.

A new British locality for beudantite [PbFe3(AsO4)(SO4)(OH)6] is recorded. The mineral is intimately associated with goethite; chemical, d.t.a., and thermogravimetric analysis data for the mixture are presented and a possible paragenesis suggested.